using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;

namespace tcp
{
    class file_server
    {
        /// <summary>
        /// The PORT
        /// </summary>
        const int PORT = 9000;
        /// <summary>
        /// The BUFSIZE
        /// </summary>
        const int BUFSIZE = 1000;

        const string IP = "10.0.0.1";

        static TcpListener serverSocket;

        /// <summary>
        /// Initializes a new instance of the <see cref="file_server"/> class.
        /// Opretter en socket.
        /// Venter på en connect fra en klient.
        /// Modtager filnavn
        /// Finder filstørrelsen
        /// Kalder metoden sendFile
        /// Lukker socketen og programmet
        /// </summary>
        private file_server ()
        {
            IPAddress ipAddress = IPAddress.Parse(IP);
            serverSocket = new TcpListener(ipAddress,PORT);
            int requestCount = 0;
            TcpClient clientSocket = default(TcpClient);
            serverSocket.Start();
            Console.WriteLine(" >> Server Started");
            clientSocket = serverSocket.AcceptTcpClient();
            Console.WriteLine(" >> Accept connection from client");

            while ((true))
            {
                try
                {
                    string serverResponse;
                    Byte[] sendBytes;
                    requestCount = requestCount + 1;
                    NetworkStream networkStream = clientSocket.GetStream();
                    byte[] bytesFrom = new byte[BUFSIZE];
                    networkStream.Read(bytesFrom, 0, (int)clientSocket.ReceiveBufferSize);
                    string dataFromClient = System.Text.Encoding.ASCII.GetString(bytesFrom);
                    if(!File.Exists(dataFromClient))
                    {
                        serverResponse = "Error: File wasn't found";
                        sendBytes = Encoding.ASCII.GetBytes(serverResponse);
                        networkStream.Write(sendBytes, 0, sendBytes.Length);
                        networkStream.Flush();
                        continue;
                    }
                    long fileSize = new System.IO.FileInfo(dataFromClient).Length;
                    sendFile(dataFromClient, fileSize, networkStream);
                    networkStream.Write(sendBytes, 0, sendBytes.Length);

                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.ToString());
                    clientSocket.Close();
                    serverSocket.Stop();
                    Console.WriteLine(" >> exit");
                    Console.ReadLine();
                }
            }
        }

        /// <summary>
        /// Sends the file.
        /// </summary>
        /// <param name='fileName'>
        /// The filename.
        /// </param>
        /// <param name='fileSize'>
        /// The filesize.
        /// </param>
        /// <param name='io'>
        /// Network stream for writing to the client.
        /// </param>
        private void sendFile (String fileName, long fileSize, NetworkStream io)
        {
            using(FileStream fs = new FileStream(fileName,FileMode.Open,FileAccess.Read))
            {
                byte[] buf = new byte[BUFSIZE];
                int offset = 0;
                while((offset += fs.Read(buf,offset,BUFSIZE)) <= fileSize )
                {
                    io.Write(buf, 0, BUFSIZE);
                }
            }
        }

        /// <summary>
        /// The entry point of the program, where the program control starts and ends.
        /// </summary>
        /// <param name='args'>
        /// The command-line arguments.
        /// </param>
        public static void Main (string[] args)
        {
            Console.WriteLine ("Server starts...");
            new file_server();
        }
    }
}